HBOT has also been shown to reduce the uptake ofserotonin by pulmonary endothelial cells [233,234],and thus might function like an SSRI. In one study,HBOT demonstrated ‘‘antidepressant-like activity’’similar to that seen with some SSRI antidepressantslike fluoxetine [235]. In another studyon patients with cluster headaches, HBOT improvedpain and was shown to act through serotonergicpathways [236]. Furthermore, in an animalmodel, HBOT was shown to decrease the releaseof dopamine after cerebral injury [237]. In anotheranimal study, 90% oxygen at room air pressure(1 atm) decreased extracellular dopamine levelsin the brain [238]. Therefore, HBOT might improvethe neurotransmitter.